Cryptosporidium parvum antigens, antibodies thereto and diagnostic and therapeutic compositions thereof

ABSTRACT

Cloning and expression of genes encoding  C. parvum  antigenic polypeptides are described as are antibodies that recognize epitopes on these polypeptides. The antigenic polypeptides and antibodies thereto can be used in therapeutic compositions for the prevention and treatment of  C. parvum  infections, as well as in diagnostic methods for determining the presence of  C. parvum  infections.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/900,817, filed Sep. 13, 2007, which is a divisional of U.S. patentapplication Ser. No. 10/948,490, filed Sep. 23, 2004, now U.S. Pat. No.7,288,621, which is a continuation of U.S. patent application Ser. No.09/881,556, filed Jun. 14, 2001, now U.S. Pat. No. 6,808,900, from whichapplications priority is claimed pursuant to 35 U.S.C. §120. U.S. patentapplication Ser. No. 09/881,556 claims the benefit under 35 U.S.C.§119(e) of U.S. Provisional Patent Application. No. 60/212,083, filedJun. 15, 2000. All of the foregoing applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The present invention relates generally to protozoan antigens and genesencoding the same. More particularly, the present invention pertains tothe cloning, expression and characterization of polypeptides fromCryptosporidium parvum (C. parum) and antibodies directed to thesepolypeptides. The invention also pertains to use of the antigenicpolypeptides and antibodies in therapeutic and diagnostic compositions.

BACKGROUND

Cryptosporidium parvum (C. parum) is a coccidian protozoan that infectsa wide variety of vertebrates, including humans. C. parvum can beacquired directly from animal-to-human contact, human-to-human contactor indirectly in fomites, water and sometimes food. Current et al.(1983) N. Engl. J. Med. 308:1252-1257; Centers of Disease Control (1984)“Cryptosporidiosis among children attending day-care centers—Georgia,Pennsylvania, Michigan, California, New Mexico” 33:599-601; Wolfson etal. (1995) N. Engl. J. Med. 312:1278-1281. Acquisition of infectionoccurs by ingestion of oocysts which excyst in the upper small bowelreleasing four infective sporozoites. The sporozoites penetrate thelining enterocyte and undergo either sexual or asexual reproduction,gametogony and merogony, respectively. The products of either form ofreproduction are capable of sustaining infection in man. Navin et al.(1984) Rev. Infect. Dis. 6:313-327.

The reservoir of C. parvum is in wild and domestic animals, particularlycattle (Tzipori (1983) Microbiol. Rev. 47:84-96) and this pathogencauses significant economic losses to the farm industry annually.Clinical manifestations of C. parvum infection may include waterydiarrhea, crampy epigrastric abdominal pain, malabsorption of nutrientsand weight loss, anorexia and malaise. The disease is usually selflimited in the immunocompetent host but can be life threatening in theimmunodeficient host, particularly in human patients with advanced HumanImmunodeficiency Virus (HIV) infection. Current et al. (1983), supra;Wolfson et al. (1985) N. Engl. J. Med. 312:1278-1281; Soave (1988)Infect. Dis. Clin. N. Amer. 2:485.

The absence of an adequate in vitro culture system has severely limitedthe investigation of C. parvum. Furthermore, use of animal models,particularly mice, is of limited value because adult mice are notnormally susceptible to infection with C. parvum.

Several groups have reported the cloning and characterization of C.parvum antigens and genes using a variety of techniques. See, e.g.,Jenkins et al. (1993) Infect. Immun. 61:2377-2382; Jenkins et al. (1995)Mol. Biochem. Parasitol. 71:149-152; Peterson et al. (1992) Infect.Immun. 60:2343-2348; Ranucci et al. (1993) Infect. Immun. 61:2347-2356.

After natural infection, a wide variety of cryptosporidial proteins arerecognized by human and animal immune sera. Ortega-Mora et al. (1992)Infect. Immun. 60:3442-3445; Campbell et al. (1983) J. Clin. Microbiol.18:165-169; Whitmire et al. (1991) Infect. Immun. 59:990-995; Nina etal. (1992) Infect. Immun. 60:1509-1513; Peeters et al. (1992) Infect.Immun. 60:2309-2316. The components that constitute protective immunityare unknown although, like most obligate intracellular coccidianprotozoa, both the cellular and humoral arms of the immune response arelikely to play important roles in the genesis of protective immunity.Lillehoj et al. (1994) Parasit. Today 10:10-16. Use of recombinant C.parvum proteins in vaccine compositions has also been described. See,e.g., U.S. Pat. No. 5,591,434. However, no consistently effectivetherapy of vaccination exists, perhaps because the antigens used in thevaccines were identified from non-human sources.

There have also been several attempts to identify antibodies thatneutralize C. parvum infection. In human studies, orally administeredhyperimmune bovine colostrum has been found to alter the natural historyof C. parvum by decreasing the excretion of oocysts, reducing the levelof diarrhea, and in a smaller number of cases, clearing the parasitefrom stool. Tzipori et al. (1986) Br. Med. J. 293:1276-1277; Nord et al.(1989) “Treatment of AIDS associated cryptosporidiosis with hyperimmunecolostrum from cows vaccinated with Cryptosporidium”, FifthInternational Conference on AIDS, Montreal, Quebec, May 1989; Ungar etal. (1990) Gastroenterology 98:486-489. Several antigens that arerecognized by sera after natural infection have been characterized andhave been shown to be the targets of neutralizing antibody in the murinesystem. Arrowood et al. (1989) Infect. Immun. 57:2283-2288; Bjorneby etal. (1991) Infect. Immun. 59:1172-1176; Doyle et al. (1993) Infect.Immun. 61:4079-4084; Riggs et al. (1989) J. Immunol. 143:1340-1345;Peterson et al. (1992) Infect. Immun. 60:2343-2348. However, animalstudies in the murine model of infection indicate only a partiallyprotective role when these antibodies are orally administered.

Thus, there remains a need for the identification of antibodies usefulin diagnostic and therapeutic compositions and for the identification ofantigens from C. parvum that react with human sera and for diagnosticand therapeutic compositions and methods using these antigens.

DISCLOSURE OF THE INVENTION

The present invention is based on the discovery of genes encoding C.parvum antigenic polypeptides, the characterization of thesepolypeptides and antibodies that recognize epitopes of thesepolypeptides. The proteins encoded by the genes have been recombinantlyproduced and these polypeptides, immunogenic fragments and analogsthereof, and/or chimeric proteins including the same, can be used,either alone or in combination with other C. parvum antigens, in novelsubunit vaccines to provide protection from cryptosporidial infection inmammalian subjects. Antibodies generated against these proteins, and/orfragments thereof, either alone or in combination with other therapeuticagents, can be used in novel therapeutic agents for mammalian subjects.Furthermore, the antigens and antibodies can be used as diagnostics.

Accordingly, in one embodiment, the subject invention is directed to anisolated nucleic acid molecule comprising a coding sequence for animmunogenic C. parvum antigenic polypeptide selected from the groupconsisting of (a) a C. parvum antigenic polypeptide AG1 and (b) a C.parvum antigenic polypeptide AG2, or a fragment of the nucleic acidmolecule comprising at least 15 nucleotides.

In additional embodiments, the invention is directed to recombinantvectors including the nucleic acid molecules, host cells transformedwith these vectors, and methods of recombinantly producing C. parvumantigenic polypeptides.

In still further embodiments, the subject invention is directed tovaccine compositions comprising a pharmaceutically acceptable vehicleand an immunogenic C. parvum antigenic polypeptide selected from thegroup consisting of (a) a C. parvum antigenic polypeptide AG1, (b) a C.parvum antigenic polypeptide AG2 and (c) an immunogenic fragment of (a)or (b) comprising at least 5 amino acids, as well as methods ofpreparing the vaccine compositions.

In other embodiments, the invention is directed to therapeuticcompositions comprising a pharmaceutically acceptable vehicle and anantibody (e.g., monoclonal antibody 1101 or 222) that recognize animmunogenic C. parvum antigenic polypeptide selected from the groupconsisting of (a) a C. parvum antigenic polypeptide AG1, (b) a C. parvumantigenic polypeptide AG2 and (c) an immunogenic fragment of (a) or (b)comprising at least 5 amino acids, as well as methods of preparing thetherapeutic compositions.

In yet other embodiments, the present invention is directed to methodsof treating or preventing C. parvum infections in a mammalian subject.The method comprises administering to the subject a therapeuticallyeffective amount of the above vaccine or therapeutic compositions.

In additional embodiments, the invention is directed to methods ofdetecting C. parvum antibodies in a biological sample comprising:

(a) providing a biological sample;

(b) reacting the biological sample with a C. parvum antigenicpolypeptide selected from the group consisting of (a) a C. parvumantigenic polypeptide AG1, (b) a C. parvum antigenic polypeptide AG2 and(c) an immunogenic fragment of (a) or (b) comprising at least 5 aminoacids, under conditions which allow C. parvum antibodies, when presentin the biological sample, to bind to the C. parvum antigenic polypeptideto form an antibody/antigen complex; and

(c) detecting the presence or absence of the complex,

thereby detecting the presence or absence of C. parvum antibodies in thesample.

In additional embodiments, the invention is directed to methods ofdetecting C. parvum antigens in a biological sample comprising:

(a) providing a biological sample;

(b) reacting the biological sample with an antibody that recognizes a C.parvum antigenic polypeptide selected from the group consisting of (a) aC. parvum antigenic polypeptide AG1, (b) a C. parvum antigenicpolypeptide AG2 and (c) an immunogenic fragment of (a) or (b) comprisingat least 5 amino acids, under conditions which allow C. parvum antigens,when present in the biological sample, to bind to the C. parvum antibodyto form an antibody/antigen complex; and

(c) detecting the presence or absence of the complex,

thereby detecting the presence or absence of C. parvum antigens in thesample.

In yet further embodiments, the invention is directed to animmunodiagnostic test kit for detecting C. parvum infection. The testkit comprises a C. parvum antigenic polypeptide selected from the groupconsisting of (a) a C. parvum antigenic polypeptide AG1, (b) a C. parvumantigenic polypeptide AG2 and (c) an immunogenic fragment of (a) or (b)comprising at least 5 amino acids, and instructions for conducting theimmunodiagnostic test. The invention is also directed toimmunodiagnostic test kits comprising an antibody that recognizes a C.parvum antigenic polypeptide selected from the group consisting of (a) aC. parvum antigenic polypeptide AG1, (b) a C. parvum antigenicpolypeptide AG2 and (c) an immunogenic fragment of (a) or (b) comprisingat least 5 amino acids, and instructions for conducting theimmunodiagnostic test.

These and other embodiments of the present invention will readily occurto those of ordinary skill in the art in view of the disclosure herein.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1B show the nucleotide sequence (SEQ ID NO:1) and correspondingamino acid sequence (SEQ ID NO:2) of C. parvum AG1.

FIGS. 2A-2B show the nucleotide sequence (SEQ ID NO:3) and correspondingamino acid sequence (SEQ ID NO:4) of C. parvum AG2.

FIGS. 3A and 3B show immunoblots of affinity purified human antibodiesand monoclonal antibody 1101 directed against total, soluble andinsoluble cryptosporidial proteins. FIG. 3A shows that human antibodiesrecognize a faint band in total protein at approximately 22 kDa.Monoclonal antibody 1101 recognized a 22 kd band (FIG. 3B, lane 1) ininsoluble cryptosporidial protein and FIG. 3B, lane 2 shows that 1101recognized three bands (22, 32 and 96 kDa) in soluble cryptosporidialprotein.

FIGS. 4A and 4B show immunoblots of affinity purified human antibodiesand monoclonal antibody 222 directed against total, soluble andinsoluble cryptosporidial proteins. FIG. 4A shows that human antibodiesrecognize three bands in total protein at approximately 17, 34 and 84kDa. Monoclonal antibody 222 recognized no bands (FIG. 4B, lane 1) ininsoluble cryptosporidial protein and five bands at approximately 6, 10,22, 34 and 84 kDa in soluble cryptosporidial protein. (FIG. 4B, lane 2).

FIGS. 5A-5F show immunolocalization in C. parvum oocysts and sporozoitesof antigens recognized by mAbs 1101, 222 and JB1. FIG. 5A shows that JB1(directed again human integrin) non-specifically labeled slidepreparations. FIG. 5B shows that mAb 1101 (directed against AG1)intensely stained in a diffuse pattern single and pairs of oocysts. FIG.5C shows that mAb 222 (directed against AG2) stained single oocysts andclumps in a ring-like pattern. FIG. 5D shows that sporozoites were notvisualizable when stained with JB1. FIG. 5E shows that mAb 1101 stainedsporozoites in an even staining pattern and FIG. 5F shows that mAb 222detected sporozoites with an intense pattern.

FIG. 6 depicts the effect of increasing concentrations of mAbs 1101 and222 compared to control mAb 2F12 on sporozoite invasion of HT-29 cells.

FIG. 7 depicts the effect of combinations of mAbs 1101 and 222 onsporozoite invasion of HT-29 cells.

DETAILED DESCRIPTION

The practice of the present invention will employ, unless otherwiseindicated, conventional techniques of molecular biology, microbiology,recombinant DNA technology, and immunology, which are within the skillof the art. Such techniques are explained fully in the literature. See,e.g., Sambrook, Fritsch & Maniatis, Molecular Cloning: A LaboratoryManual, Vols. I, II and III, Second Edition (1989); Perbal, B., APractical Guide to Molecular Cloning (1984); Harlow, E., et al.,Antibodies: A Laboratory Manual, Cold Spring Harbor Press, Cold SpringHarbor, N.Y. (1988); the series, Methods In Enzymology (S. Colowick andN. Kaplan eds., Academic Press, Inc.); and Handbook of ExperimentalImmunology, Vols. I-IV (D. M. Weir and C. C. Blackwell eds., 1986,Blackwell Scientific Publications).

All publications, patents and patent applications cited herein, whethersupra or infra, are hereby incorporated by reference in their entirety.

The following amino acid abbreviations are used throughout the text:

Alanine: Ala (A) Arginine: Arg (R)

Asparagine: Asn (N) Aspartic acid: Asp (D)

Cysteine: Cys (C) Glutamine: Gln (O)

Glutamic acid: Glu (E) Glycine: Gly (G)

Histidine: H is (H) Isoleucine: Ile (I)

Leucine: Leu (L) Lysine: Lys (K)

Methionine: Met (M) Phenylalanine: Phe (F)

Proline: Pro (P) Serine: Ser (S)

Threonine: Thr (T) Tryptophan: Tip (W)

Tyrosine: Tyr (Y) Valine: Val (V)

A. Definitions

In describing the present invention, the following terms will beemployed, and are intended to be defined as indicated below.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a”, “an” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to “a C. parvum polypeptide” includes a mixture of two or moresuch proteins, and the like. Furthermore, the derived polypeptide ornucleotide sequences need not be physically derived from the organism orgene of interest, but may be generated in any manner, including forexample, chemical synthesis, isolation (e.g., from C. parvum) or byrecombinant production, based on the information provided herein.Additionally, the term intends proteins having amino acid sequencessubstantially homologous (as defined below) to contiguous amino acidsequences encoded by the genes, which display immunological activityand/or are recognized by a biological sample obtained from an infectedsubject.

Thus, the terms “polypeptide” and “protein” are used interchangeably tointend full-length, as well as immunogenic, truncated and partialsequences, and active analogs and precursor forms of the polypeptides.Similarly, the terms “polynucleotide” and “nucleotide sequence” are usedinterchangeably to intend nucleotide fragments of the gene that includeat least about 8 contiguous base pairs, more preferably at least about10-20 contiguous base pairs (or any value therebetween), and mostpreferably at least about 25 to 50 (or any value therebetween), or more,contiguous base pairs of the gene. Such fragments are useful as probesand in diagnostic methods, discussed more fully below.

The terms also include polypeptides in neutral form or in the form ofbasic or acid addition salts depending on the mode of preparation. Suchacid addition salts may involve free amino groups and basic salts may beformed with free carboxyls. Pharmaceutically acceptable basic and acidaddition salts are discussed further below. In addition, the proteinsmay be modified by combination with other biological materials such aslipids (both those occurring naturally with the molecule or other lipidsthat do not destroy immunological activity) and saccharides, or by sidechain modification, such as acetylation of amino groups, phosphorylationof hydroxyl side chains, oxidation of sulfhydryl groups, glycosylationof amino acid residues, as well as other modifications of the encodedprimary sequence.

The polypeptide and polynucleotides of the invention therefore encompassdeletions, additions and substitutions to the sequence, so long as thepolypeptide product functions to produce an immunological response asdefined herein. In this regard, particularly preferred substitutionswill generally be conservative in nature, i.e., those substitutions thattake place within a family of amino acids. For example, amino acids aregenerally divided into four families: (1) acidic—aspartate andglutamate; (2) basic—lysine, arginine, histidine; (3) non-polar—alanine,valine, leucine, isoleucine, proline, phenylalanine, methionine,tryptophan; and (4) uncharged polar—glycine, asparagine, glutamine,cystine, serine threonine, tyrosine. Phenylalanine, tryptophan, andtyrosine are sometimes classified as aromatic amino acids. For example,it is reasonably predictable that an isolated replacement of leucinewith isoleucine or valine, or vice versa; an aspartate with a glutamateor vice versa; a threonine with a serine or vice versa; or a similarconservative replacement of an amino acid with a structurally relatedamino acid, will not have a major effect on the biological activity.Proteins having substantially the same amino acid sequence as thereference molecule, but possessing minor amino acid substitutions thatdo not substantially affect the immunogenicity of the protein, aretherefore within the definition of the reference polypeptide. Forexample, molecules having between about 20 and 15 substitutions per 100amino acids, or less than about 10 substitutions per 100 amino acids, orbetween about 5 and 3 substitutions per 100 amino acids that retaintheir biological activity (e.g., immunogenicity) are within thisdefinition.

An “isolated” nucleic acid molecule is a nucleic acid molecule separateand discrete from the whole organism with which the molecule is found innature; or a nucleic acid molecule devoid, in whole or part, ofsequences normally associated with it in nature; or a sequence, as itexists in nature, but having heterologous sequences (as defined below)in association therewith.

By “subunit vaccine composition” is meant a composition containing atleast one immunogenic polypeptide, but not all antigens, derived from orhomologous to an antigen from a pathogen of interest. Such a compositionis substantially free of intact pathogen cells or particles, or thelysate of such cells or particles. Thus, a “subunit vaccine composition”is prepared from at least partially purified (preferably substantiallypurified) immunogenic polypeptides from the pathogen, or recombinantanalogs thereof. A subunit vaccine composition can comprise the subunitantigen or antigens of interest substantially free of other antigens orpolypeptides from the pathogen.

The term “epitope” refers to the site on an antigen or hapten to whichspecific B cells and/or T cells respond. The term is also usedinterchangeably with “antigenic determinant” or “antigenic determinantsite.” Antibodies that recognize the same epitope can be identified in asimple immunoassay showing the ability of one antibody to block thebinding of another antibody to a target antigen.

An “immunological response” to a composition or vaccine is thedevelopment in the host of a cellular and/or antibody-mediated immuneresponse to the composition or vaccine of interest. Usually, an“immunological response” includes but is not limited to one or more ofthe following effects: the production of antibodies, B cells, helper Tcells, suppressor T cells, and/or cytotoxic T cells and/or γδ T cells,directed specifically to an antigen or antigens included in thecomposition or vaccine of interest. Preferably, the host will displayeither a therapeutic or protective immunological response such thatresistance to new infection will be enhanced and/or the clinicalseverity of the disease reduced. Such protection will be demonstrated byeither a reduction or lack of symptoms normally displayed by an infectedhost and/or a quicker recovery time.

The terms “immunogenic” protein or polypeptide refer to an amino acidsequence which elicits an immunological response as described above. An“immunogenic” protein or polypeptide, as used herein, includes thefull-length sequence of the C. parvum polypeptides in question, with orwithout any signal sequences, membrane anchor domains, analogs thereof,or immunogenic fragments thereof. By “immunogenic fragment” is meant afragment of which includes one or more epitopes and thus elicits theimmunological response described above. Such fragments can be identifiedusing any number of epitope mapping techniques, well known in the art.See, e.g., Epitope Mapping Protocols in Methods in Molecular Biology,Vol. 66 (Glenn E. Morris, Ed., 1996) Humana Press, Totowa, N.J. Forexample, linear epitopes may be determined by e.g., concurrentlysynthesizing large numbers of peptides on solid supports, the peptidescorresponding to portions of the protein molecule, and reacting thepeptides with antibodies while the peptides are still attached to thesupports. Such techniques are known in the art and described in, e.g.,U.S. Pat. No. 4,708,871; Geysen et al. (1984) Proc. Natl. Acad. Sci. USA81:3998-4002; Geysen et al. (1986) Molec. Immunol. 23:709-715, allincorporated herein by reference in their entireties. Similarly,conformational epitopes are readily identified by determining spatialconformation of amino acids such as by, e.g., x-ray crystallography and2-dimensional nuclear magnetic resonance. See, e.g., Epitope MappingProtocols, supra. Antigenic regions of proteins can also be identifiedusing standard antigenicity and hydropathy plots, such as thosecalculated using, e.g., the Omiga version 1.0 software program availablefrom the Oxford Molecular Group. This computer program employs theHopp/Woods method, Hopp et al., Proc. Natl. Acad. Sci USA (1981)78:3824-3828 for determining antigenicity profiles, and theKyte-Doolittle technique, Kyte et al., J. Mol. Biol. (1982) 157:105-132for hydropathy plots.

Immunogenic fragments, for purposes of the present invention, willusually include at least about 3 amino acids, preferably at least about5 amino acids, more preferably at least about 10-15 amino acids, andmost preferably 25 or more amino acids, of the parent C. parvumantigenic molecule. There is no critical upper limit to the length ofthe fragment, which may comprise nearly the full-length of the proteinsequence, or even a fusion protein comprising two or more epitopes ofAG1 and/or AG2.

“Native” proteins or polypeptides refer to proteins or polypeptidesisolated from the source in which the proteins naturally occur.“Recombinant” polypeptides refer to polypeptides produced by recombinantDNA techniques; i.e., produced from cells transformed by an exogenousDNA construct encoding the desired polypeptide. “Synthetic” polypeptidesare those prepared by chemical synthesis.

A “vector” is a replicon, such as a plasmid, phage, or cosmid, to whichanother DNA segment may be attached so as to bring about the replicationof the attached segment.

A DNA “coding sequence” or a “nucleotide sequence encoding” a particularprotein, is a DNA sequence which is transcribed and translated into apolypeptide in vitro or in vivo when placed under the control ofappropriate regulatory elements. The boundaries of the coding sequenceare determined by a start codon at the 5′ (amino) terminus and atranslation stop codon at the 3′ (carboxy) terminus. A coding sequencecan include, but is not limited to, procaryotic sequences, cDNA fromeucaryotic mRNA, genomic DNA sequences from eucaryotic (e.g., mammalian)DNA, and even synthetic DNA sequences. A transcription terminationsequence will usually be located 3′ to the coding sequence.

DNA “control elements” refers collectively to promoters, ribosomebinding sites, polyadenylation signals, transcription terminationsequences, upstream regulatory domains, enhancers, and the like, whichcollectively provide for the transcription and translation of a codingsequence in a host cell. Not all of these control sequences need alwaysbe present in a recombinant vector so long as the desired gene iscapable of being transcribed and translated.

“Operably linked” refers to an arrangement of elements wherein thecomponents so described are configured so as to perform their usualfunction. Thus, control elements operably linked to a coding sequenceare capable of effecting the expression of the coding sequence. Thecontrol elements need not be contiguous with the coding sequence, solong as they function to direct the expression thereof. Thus, forexample, intervening untranslated yet transcribed sequences can bepresent between a promoter and the coding sequence and the promoter canstill be considered “operably linked” to the coding sequence.

A control element, such as a promoter, “directs the transcription” of acoding sequence in a cell when RNA polymerase will bind the promoter andtranscribe the coding sequence into mRNA, which is then translated intothe polypeptide encoded by the coding sequence.

A “host cell” is a cell which has been transformed, or is capable oftransformation, by an exogenous nucleic acid molecule.

A cell has been “transformed” by exogenous DNA when such exogenous DNAhas been introduced inside the cell membrane. Exogenous DNA may or maynot be integrated (covalently linked) into chromosomal DNA making up thegenome of the cell. In procaryotes and yeasts, for example, theexogenous DNA may be maintained on an episomal element, such as aplasmid. With respect to eucaryotic cells, a stably transformed cell isone in which the exogenous DNA has become integrated into the chromosomeso that it is inherited by daughter cells through chromosomereplication. This stability is demonstrated by the ability of theeucaryotic cell to establish cell lines or clones comprised of apopulation of daughter cells containing the exogenous DNA.

“Homology” refers to the percent identity between two polynucleotide ortwo polypeptide moieties. Two nucleotide, or two polypeptide sequences,are “substantially homologous” to each other when the sequences exhibitat least about 80%-85%, preferably at least about 90%, and mostpreferably at least about 95%-98% sequence identity over a definedlength of the molecules. As used herein, substantially homologous alsorefers to sequences showing complete identity to the specified DNA orpolypeptide sequence.

Techniques for determining nucleic acid and amino acid “sequenceidentity” or “sequence homology” also are known in the art. Typically,such techniques include determining the nucleotide sequence of the mRNAfor a gene and/or determining the amino acid sequence encoded thereby,and comparing these sequences to a second nucleotide or amino acidsequence. In general, “identity” refers to an exactnucleotide-to-nucleotide or amino acid-to-amino acid correspondence oftwo polynucleotides or polypeptide sequences, respectively. Two or moresequences (polynucleotide or amino acid) can be compared by determiningtheir “percent identity.” The percent identity of two sequences, whethernucleic acid or amino acid sequences, is the number of exact matchesbetween two aligned sequences divided by the length of the shortersequences and multiplied by 100. An approximate alignment for nucleicacid sequences is provided by the local homology algorithm of Smith andWaterman, Advances in Applied Mathematics 2:482-489 (1981). Thisalgorithm can be applied to amino acid sequences by using the scoringmatrix developed by Dayhoff, Atlas of Protein Sequences and Structure,M. O. Dayhoff ed., 5 suppl. 3:353-358, National Biomedical ResearchFoundation, Washington, D.C., USA, and normalized by Gribskov, Nucl.Acids Res. 14(6):6745-6763 (1986).

An exemplary implementation of this algorithm to determine percentidentity of a sequence is provided by the Genetics Computer Group(Madison, Wis.) in the “BestFit” utility application. The defaultparameters for this method are described in the Wisconsin SequenceAnalysis Package Program Manual, Version 8 (1995) (available fromGenetics Computer Group, Madison, Wis.). Another method of establishingpercent identity is to use the MPSRCH package of programs copyrighted bythe University of Edinburgh, developed by John F. Collins and Shane S.Sturrok, and distributed by IntelliGenetics, Inc. (Mountain View,Calif.). From this suite of packages the Smith-Waterman algorithm can beemployed where default parameters are used for the scoring table (forexample, gap open penalty of 12, gap extension penalty of one, and a gapof six). From the data generated the “Match” value reflects “sequenceidentity.” Other suitable programs for calculating the percent identityor similarity between sequences are generally known in the art, forexample, another alignment program is BLAST, used with defaultparameters. For example, BLASTN and BLASTP can be used to determinepercent identity using the following default parameters: geneticcode=standard; filter=none; strand=both; cutoff=60; expect=10;Matrix=BLOSUM62; Descriptions=50 sequences; sort by=HIGH SCORE;Databases=non-redundant, GenBank+EMBL+DDBJ+PDB+GenBank CDStranslations+Swiss protein+Spupdate+PIR. Details of these programs canbe found at the following internet address:http://www.ncbi.nlm.gov/cgi-bin/BLAST. Another example of determiningpercent identity is using the Smith-Waterman search algorithm (TimeLogic, Incline Village, Nev.), with the following exemplary parameters:weight matrix=nuc4×4 hb; gap opening penalty=20, gap extensionpenalty=5.

Alternatively, for nucleotides, homology can be determined byhybridization of polynucleotides under conditions which form stableduplexes between homologous regions, followed by digestion withsingle-stranded-specific nuclease(s), and size determination of thedigested fragments. DNA sequences that are substantially homologous canbe identified in a Southern hybridization experiment under, for example,stringent conditions, as defined for that particular system. Forexample, stringent hybridization conditions can include 50% formamide,5×Denhardt's Solution, 5×SSC, 0.1% SDS and 100 μg/ml denatured salmonsperm DNA and the washing conditions can include 2×SSC, 0.1% SDS at 37°C. followed by 1×SSC, 0.1% SDS at 68° C. Defining appropriatehybridization conditions is within the skill of the art. See, e.g.,Sambrook et al., supra; DNA Cloning, supra; Nucleic Acid Hybridization,supra. For amino acids, homology can also be determined by aligning twoor more amino acids sequences (as described above) and determining thenumber of substitutions and/or deletions. Typically, amino acidsequences are substantially homologous when between about 20 and 15amino acid substitutions or deletions are made per 100 amino acids, morepreferably between about 10 amino acid substitutions or deletions andeven more preferably between about 5 and 3 amino acid substitutions ordeletions. As used herein, substantially homologous also refers tosequences showing complete identity to the specified DNA or polypeptidesequence.

By the term “degenerate variant” is intended a polynucleotide containingchanges in the nucleic acid sequence thereof, that encodes a polypeptidehaving the same amino acid sequence as the polypeptide encoded by thepolynucleotide from which the degenerate variant is derived.

The term “functionally equivalent” intends that the amino acid sequenceof an antigenic C. parvum polypeptide is one that will elicit asubstantially equivalent or enhanced immunological response, as definedabove, as compared to the response elicited by an antigenic polypeptidehaving identity with the AG1 and AG2 polypeptides, or immunogenicportions thereof. The term also includes antibodies, or fragmentsthereof, that will elicit a substantially equivalent or enhancedneutralizing or other therapeutic response, as compared to monoclonalantibodies 1101 and 222. “1101” refers to a particular monoclonalantibody raised against the antigenic C. parvum polypeptide with thedesignation AG1. The generation and characterization of 1101 isdescribed in the Examples. Similarly, “222” refers to a particularmonoclonal antibody raised against the antigenic C. parvum polypeptidewith the designation AG2. The generation and characterization of 222 isdescribed in the Examples.

A “heterologous” region of a DNA construct is an identifiable segment ofDNA within or attached to another DNA molecule that is not found inassociation with the other molecule in nature. Thus, when theheterologous region encodes a bacterial gene, the gene will usually beflanked by DNA that does not flank the bacterial gene in the genome ofthe source bacteria. Another example of the heterologous coding sequenceis a construct where the coding sequence itself is not found in nature(e.g., synthetic sequences having codons different from the nativegene). Allelic variation or naturally occurring mutational events do notgive rise to a heterologous region of DNA, as used herein.

The terms “treatment” and “therapeutic” as used herein refer to either(i) the prevention of infection or reinfection (prophylaxis), including,for example, vaccines or (ii) the reduction or elimination of symptomsof the disease of interest (therapy).

As used herein, a “biological sample” refers to a sample of tissue orfluid isolated from a subject, including but not limited to, forexample, blood, plasma, serum, fecal matter, urine, bone marrow, bile,spinal fluid, lymph fluid, samples of the skin, external secretions ofthe skin, respiratory, intestinal, and genitourinary tracts, tears,saliva, milk, blood cells, organs, biopsies and also samples of in vitrocell culture constituents including but not limited to conditioned mediaresulting from the growth of cells and tissues in culture medium, e.g.,recombinant cells, and cell components.

As used herein, the terms “label” and “detectable label” refer to amolecule capable of detection, including, but not limited to,radioactive isotopes, fluorescers, chemiluminescers, enzymes, enzymesubstrates, enzyme cofactors, enzyme inhibitors, chromophores, dyes,metal ions, metal sols, ligands (e.g., biotin or haptens) and the like.The term “fluorescer” refers to a substance or a portion thereof whichis capable of exhibiting fluorescence in the detectable range.Particular examples of labels which may be used under the inventioninclude fluorescein, rhodamine, dansyl, umbelliferone, Texas red,luminol, NADPH and α-β-galactosidase.

The terms “individual” and “subject” are used interchangeably herein torefer to any member of the subphylum cordata, including, withoutlimitation, humans and other primates, including non-human primates suchas chimpanzees and other apes and monkey species; farm animals such ascattle, sheep, pigs, goats and horses; domestic mammals such as dogs andcats; laboratory animals including rodents such as mice, rats and guineapigs; birds, including domestic, wild and game birds such as chickens,turkeys and other gallinaceous birds, ducks, geese, and the like. Theterms do not denote a particular age. Thus, both adult and newbornindividuals are intended to be covered. The methods described herein areintended for use in any of the above vertebrate species.

B. General Methods

Central to the present invention is the discovery of genes encoding twoC. parvum antigenic polypeptides (termed “AG1” and “AG2” respectivelyherein) and antibodies to these polypeptides which have been shown tohave neutralizing effects on C. parvum infection in mammalian subjects.In particular, the genes for C. parvum antigenic polypeptide 1 (“ag1”)and C. parvum antigenic polypeptide 2 (“ag2”) have been isolated,sequenced and characterized, and the protein sequences for AG1 and AG2deduced therefrom. Monoclonal antibodies have been generated against therecombinantly produced proteins and have been shown to have neutralizingactivity against the infective sporozoite of C. parvum.

The cDNA and predicted amino acid sequences of AG1 and AG2 are shown inFIGS. 1A-1B and 2A-2B, respectively. Perfect and imperfect consensuspolyadenylation signals are underlined and N-glycosylation sites are inbold face type. The DNA sequence of AG1 is also shown in SEQ ID NO:1,while SEQ ID NO:3 shows the complete DNA sequence of AG2. The predictedamino acid sequences for AG1 and AG2 are shown in SEQ ID NOs:1 and 2 andSEQ ID NOs:3 and 4, respectively.

As described in the examples, full-length ag1, depicted at nucleotidepositions 8-394, inclusive, of FIG. 1A, encodes a full-length AG1protein of approximately 129 amino acids, shown as amino acids 1-129,inclusive, of FIG. 1A (SEQ ID NO:2). The 3′ untranslated region is 945nucleotides long, from positions 395-1338 of FIG. 1A (SEQ ID NO:1).Imperfect polyadenylation signals occur at positions 1241-1245 and1307-1311. The sequence has been assigned GenBank Accession NumberAF178459. The protein encoded by the predicted open reading frame (ORF)has a predicted molecular weight of about 15 kDa. The predictedisoelectric point is pH 9.6 and 44% of the predicted amino acid residuesare hydrophobic. Two N-linked glycosylation sites have been identifiedat amino acid residues 36-38 and 71-73.

Full-length ag2, depicted at nucleotide positions 9-587, inclusive, ofFIG. 1B, encodes a full-length AG2 protein of approximately 193 aminoacids, shown as amino acids 1-193, inclusive, of FIG. 1B (SEQ ID NO:4).The 3′ untranslated region is 712 nucleotides long, from positions588-1298 of FIG. 1B (SEQ ID NO:2). Imperfect polyadenylation signalsoccur at positions 945-949 and 1141-1145. The sequence has been assignedGenBank Accession Number AF178460. The protein encoded by the predictedopen reading frame (ORF) has a predicted molecular weight of about 21.8kDa. The predicted isoelectric point is pH 6.23 and 36% of the predictedamino acid residues are hydrophobic. Two N-linked glycosylation siteswere identified at amino acid residues 36-38 and 51-53.

The C. parvum polynucleotides, antigenic peptides, immunogenic fragmentsthereof or chimeric proteins including one or more epitopes of AG1 andAG2, can be provided, either alone or in combination, in subunit vaccinecompositions or other therapeutic compositions to treat or preventinfections caused by C. parvum. Similarly, antibodies generated to AG1or AG2, for example, monoclonal antibodies 1101 and 222, and antibodiescross-reactive therewith, can be provided, alone or in combination, incompositions to prevent, treat, or neutralize infections caused by C.parvum.

In addition to use in therapeutic compositions, proteins and fragmentsthereof, antibodies thereto, and polynucleotides coding therefor, can beused as diagnostic reagents to detect the presence of infection in amammalian subject. Similarly, the polynucleotides encoding the proteinscan be cloned and used to design probes to detect and isolate homologousgenes in other protozoans. For example, fragments comprising at leastabout 15-20 nucleotides, more preferably at least about 20-50nucleotides, and most preferably about 60-100 or more nucleotides, willfind use in these embodiments. The C. parvum antigenic polypeptides alsofind use in purifying antibodies for diagnostic and therapeutic uses.

C. parvum antigenic polypeptides can be used in vaccine compositionseither alone or in combination with bacterial, fungal, viral or otherprotozoal antigens. These antigens can be provided separately or even asfusion proteins comprising one or more epitopes of the antigenicpolypeptides fused together and/or to one or more of the above antigens.For example, other immunogenic proteins from C. parvum can be used inthe subject therapeutic compositions. Antibodies directed to thesepolypeptides can also be used as therapeutics. Antibodies 1101 and 222have each been shown to have a neutralizing effect on C. parvuminfection.

Production of Antigenic Polypeptides

The above described antigenic polypeptides and active fragments, analogsand chimeric proteins derived from the same, can be produced by avariety of methods. Specifically, the polypeptides can be isolateddirectly from protozoa (oocytes, sporozoites or adults) which expressthe same, using standard purification techniques. See, e.g. Tilley etal. (1991) Infect. Immun. 59:1002-1007. The desired proteins can then befurther purified i.e. by column chromatography, HPLC, immunoadsorbenttechniques or other conventional methods well known in the art.

Alternatively, the proteins can be recombinantly produced as describedherein. As explained above, these recombinant products can take the formof partial protein sequences, full-length sequences, precursor formsthat include signal sequences, mature forms without signals, or evenfusion proteins (e.g., with an appropriate leader for the recombinanthost, or with another subunit antigen sequence for C. parvum or anotherpathogen).

The ag1 and ag2-encoding sequences of the present invention can beisolated based on the ability of the protein products to bind toantibodies present in an infected sample, using detection assays asdescribed below. Thus, gene libraries can be constructed and theresulting clones used to transform an appropriate host cell. Coloniescan be pooled and screened for clones having the ability to bind C.parvum antibodies. Colonies can be screened using polyclonal serum ormonoclonal antibodies to the C. parvum proteins.

Alternatively, once the amino acid sequences are determined,oligonucleotide probes which contain the codons for a portion of thedetermined amino acid sequences can be prepared and used to screengenomic or cDNA libraries for genes encoding the subject proteins. Thebasic strategies for preparing oligonucleotide probes and DNA libraries,as well as their screening by nucleic acid hybridization, are well knownto those of ordinary skill in the art. See, e.g., DNA Cloning: Vol. I,supra; Nucleic Acid Hybridization, supra; Oligonucleotide Synthesis,supra; Sambrook et al., supra. Once a clone from the screened libraryhas been identified by positive hybridization, it can be confirmed byrestriction enzyme analysis and DNA sequencing that the particularlibrary insert contains a sequence encoding an antigenic C. parvumpolypeptide or a homolog thereof. The sequences can then be furtherisolated using standard techniques and, if desired, PCR approaches orrestriction enzymes employed to delete portions of the full-lengthsequence.

Similarly, genes can be isolated directly from protozoans using knowntechniques, such as phenol extraction and the sequence furthermanipulated to produce any desired alterations. See, e.g., Sambrook etal., supra, for a description of techniques used to obtain and isolateDNA.

Alternatively, DNA sequences encoding the proteins of interest can beprepared synthetically rather than cloned. The DNA sequences can bedesigned with the appropriate codons for the particular amino acidsequence. In general, one will select preferred codons for the intendedhost if the sequence will be used for expression. The complete sequenceis assembled from overlapping oligonucleotides prepared by standardmethods and assembled into a complete coding sequence. See, e.g., Edge(1981) Nature 292:756; Nambair et al. (1984) Science 223:1299; Jay etal. (1984) J. Biol. Chem. 259:6311.

Once coding sequences for the desired proteins have been prepared orisolated, they can be cloned into any suitable vector or replicon.Numerous cloning vectors are known to those of skill in the art, and theselection of an appropriate cloning vector is a matter of choice.Examples of recombinant DNA vectors for cloning and host cells whichthey can transform include the bacteriophage λ (E. coli), pBR322 (E.coli), pACYC177 (E. coli), pKT230 (gram-negative bacteria), pGV1106(gram-negative bacteria), pLAFR1 (gram-negative bacteria), pME290(non-E. coli gram-negative bacteria), pHV14 (E. coli and Bacillussubtilis), pBD9 (Bacillus), pIJ61 (Streptomyces), pUC6 (Streptomyces),YIp5 (Saccharomyces), YCp19 (Saccharomyces) and bovine papilloma virus(mammalian cells). See, Sambrook et al., supra; DNA Cloning, supra; B.Perbal, supra.

The gene can be placed under the control of a promoter, ribosome bindingsite (for bacterial expression) and, optionally, an operator(collectively referred to herein as “control” elements), so that the DNAsequence encoding the desired protein is transcribed into RNA in thehost cell transformed by a vector containing this expressionconstruction. The coding sequence may or may not contain a signalpeptide or leader sequence. If a signal sequence is included, it caneither be the native, homologous sequence, or a heterologous sequence.For example, the signal sequence for the particular C. parvum antigenicpolypeptide, can be used for secretion thereof, as can a number of othersignal sequences, well known in the art. Leader sequences can be removedby the host in post-translational processing. See, e.g., U.S. Pat. Nos.4,431,739; 4,425,437; 4,338,397.

Other regulatory sequences may also be desirable which allow forregulation of expression of the protein sequences relative to the growthof the host cell. Regulatory sequences are known to those of skill inthe art, and examples include those which cause the expression of a geneto be turned on or off in response to a chemical or physical stimulus,including the presence of a regulatory compound. Other types ofregulatory elements may also be present in the vector, for example,enhancer sequences.

The control sequences and other regulatory sequences may be ligated tothe coding sequence prior to insertion into a vector, such as thecloning vectors described above. Alternatively, the coding sequence canbe cloned directly into an expression vector which already contains thecontrol sequences and an appropriate restriction site.

In some cases it may be necessary to modify the coding sequence so thatit may be attached to the control sequences with the appropriateorientation; i.e., to maintain the proper reading frame. It may also bedesirable to produce mutants or analogs of the antigenic polypeptides.Mutants or analogs may be prepared by the deletion of a portion of thesequence encoding the protein, by insertion of a sequence, and/or bysubstitution of one or more nucleotides within the sequence. Techniquesfor modifying nucleotide sequences, such as site-directed mutagenesis,are described in, e.g., Sambrook et al., supra; DNA Cloning, supra;Nucleic Acid Hybridization, supra.

The expression vector is then used to transform an appropriate hostcell. A number of mammalian cell lines are known in the art and includeimmortalized cell lines available from the American Type CultureCollection (ATCC), such as, but not limited to, Chinese hamster ovary(CHO) cells, HeLa cells, baby hamster kidney (BHK) cells, monkey kidneycells (COS), human hepatocellular carcinoma cells (e.g., Hep G2),Madin-Darby bovine kidney (“MDBK”) cells, as well as others. Similarly,bacterial hosts such as E. coli, Bacillus subtilis, and Streptococcusspp., will find use with the present expression constructs. Yeast hostsuseful in the present invention include inter alia, Saccharomycescerevisiae, Candida albicans, Candida maltosa, Hansenula polymorpha,Kluyveromyces fragilis, Kluyveromyces lactic, Pichia guillerimondii,Pichia pastoris, Schizosaccharomyces pombe and Yarrowia lipolytica.Insect cells for use with baculovirus expression vectors include, interalia, Aedes aegypti, Autographa californica, Bombyx mori, Drosophilamelanogaster, Spodoptera frugiperda, and Trichoplusia ni.

Depending on the expression system and host selected, the proteins ofthe present invention are produced by culturing host cells transformedby an expression vector described above under conditions whereby theprotein of interest is expressed. The protein is then isolated from thehost cells and purified. If the expression system secretes the proteininto the growth media, the protein can be purified directly from themedia. If the protein is not secreted, it is isolated from cell lysates.The selection of the appropriate growth conditions and recovery methodsare within the skill of the art.

The proteins of the present invention may also be produced by chemicalsynthesis such as solid phase peptide synthesis, using known amino acidsequences or amino acid sequences derived from the DNA sequence of thegenes of interest. Such methods are known to those skilled in the art.See, e.g., J. M. Stewart and J. D. Young, Solid Phase Peptide Synthesis,2nd Ed., Pierce Chemical Co., Rockford, Ill. (1984) and G. Barany and R.B. Merrifield, The Peptides: Analysis, Synthesis, Biology, editors E.Gross and J. Meienhofer, Vol. 2, Academic Press, New York, (1980), pp.3-254, for solid phase peptide synthesis techniques; and M. Bodansky,Principles of Peptide Synthesis, Springer-Verlag; Berlin (1984) and E.Gross and J. Meienhofer, Eds., The Peptides: Analysis, Synthesis,Biology, supra, Vol. 1, for classical solution synthesis. Chemicalsynthesis of peptides may be preferable if a small fragment of theantigen in question is capable of raising an immunological response inthe subject of interest.

Production of Antibodies

The antigenic polypeptides of the present invention, or their fragments,can be used to produce antibodies, both polyclonal and monoclonal. Inaddition to whole antibody molecules, antibody fragments retaining theimmunological specificity of the whole antibody may also be used in thepractice of the present invention (e.g., Fab and F(ab′)₂ fragments ofIgG (Pierce)). The antibodies can be purified by standard methods toprovide antibody preparations which are substantially free of serumproteins that may affect reactivity (e.g., affinity purification (Harlowet al.)). If polyclonal antibodies are desired, a selected mammal,(e.g., mouse, rabbit, goat, horse, etc.) is immunized with an antigen ofthe present invention, or its fragment, or a mutated antigen. Serum fromthe immunized animal is collected and treated according to knownprocedures. See, e.g., Jurgen et al. (1985) J. Chrom. 348:363-370. Ifserum containing polyclonal antibodies is used, the polyclonalantibodies can be purified by immunoaffinity chromatography, using knownprocedures.

Monoclonal antibodies to the antigenic polypeptides and to the fragmentsthereof, can also be readily produced by one skilled in the art. Thegeneral methodology for making monoclonal antibodies by using hybridomatechnology is well known. Immortal antibody-producing cell lines can becreated by cell fusion, and also by other techniques such as directtransformation of B lymphocytes with oncogenic DNA, or transfection withEpstein-Barr virus. See, e.g., M. Schreier et al., Hybridoma Techniques(1980); Hammerling et al., Monoclonal Antibodies and T-cell Hybridomas(1981); Kennett et al., Monoclonal Antibodies (1980); see also U.S. Pat.Nos. 4,341,761; 4,399,121; 4,427,783; 4,444,887; 4,452,570; 4,466,917;4,472,500, 4,491,632; and 4,493,890. Panels of monoclonal antibodiesproduced against the antigenic polypeptides, or fragments thereof, canbe screened for various properties; i.e., for isotype, epitope,affinity, etc. Monoclonal antibodies are useful in purification, usingimmunoaffinity techniques, of the individual antigens which they aredirected against. Both polyclonal and monoclonal antibodies can also beused for passive immunization or can be combined with subunit vaccinepreparations to enhance the immune response. Antibodies exhibiting aneutralizing effect on C. parvum, for example monoclonal antibodies 1101and 222 described below, and others functionally equivalent to theseantibodies, are also useful in therapeutic compositions. Polyclonal andmonoclonal antibodies are also useful for diagnostic purposes.

Therapeutic Formulations and Administration

The polynucleotides, antigenic C. parvum polypeptides and antibodiesthereto of the present invention can be formulated into compositions orfor use as diagnostics, either alone, in combination and/or with otherpolynucleotides, antigens and/or antibodies, for use in immunizing ortreating subjects as described below. Methods of preparing suchformulations are described in, e.g., Remington's PharmaceuticalSciences, Mack Publishing Company, Easton, Pa., 18 Edition, 1990.Typically, therapeutic (e.g., vaccine) compositions of the presentinvention are prepared as injectables, either as liquid solutions orsuspensions. Solid forms suitable for solution in or suspension inliquid vehicles prior to injection may also be prepared. The preparationmay also be emulsified or the active ingredient encapsulated in liposomevehicles. The active (e.g., immunogenic) ingredient is generally mixedwith a compatible pharmaceutical vehicle, such as, for example, water,saline, dextrose, glycerol, ethanol, or the like, and combinationsthereof. In addition, if desired, the vehicle may contain minor amountsof auxiliary substances such as wetting or emulsifying agents and pHbuffering agents.

Adjuvants which enhance the effectiveness of the vaccine or othertherapeutic composition may also be added to the formulation. Adjuvantsmay include for example, muramyl dipeptides, pyridine, aluminumhydroxide, dimethyldioctadecyl ammonium bromide (DDA), oils,oil-in-water emulsions, saponins, cytokines, and other substances knownin the art.

The antigenic polypeptides may be linked to a carrier in order toincrease the immunogenicity thereof. Suitable carriers include large,slowly metabolized macromolecules such as proteins, including serumalbumins, keyhole limpet hemocyanin, immunoglobulin molecules,thyroglobulin, ovalbumin, and other proteins well known to those skilledin the art; polysaccharides, such as sepharose, agarose, cellulose,cellulose beads and the like; polymeric amino acids such as polyglutamicacid, polylysine, and the like; amino acid copolymers; and in-activevirus particles. Antibodies and polynucleotides may also be linked tosuch carriers prior to administration.

The polynucleotides, antigenic polyeptides or antibodies thereto may beused in their native form or their functional group content may bemodified by, for example, succinylation of lysine residues or reactionwith Cys-thiolactone. A sulfhydryl group may also be incorporated intothe carrier (or antigen) by, for example, reaction of amino functionswith 2-iminothiolane or the N-hydroxysuccinimide ester of3-(4-dithiopyridyl propionate. Suitable carriers may also be modified toincorporate spacer arms (such as hexamethylene diamine or otherbifunctional molecules of similar size) for attachment of peptides.

Other suitable carriers include cells, such as lymphocytes, sincepresentation in this form mimics the natural mode of presentation in thesubject, which gives rise to the immunized state. Alternatively, themolecules of the present invention may be coupled to erythrocytes,preferably the subject's own erythrocytes. Methods of coupling peptidesto proteins or cells are known to those of skill in the art.

Furthermore, the antigenic polypeptides (or complexes thereof) may beformulated into vaccine compositions in either neutral or salt forms.Pharmaceutically acceptable salts include the acid addition salts(formed with the free amino groups of the active polypeptides) and whichare formed with inorganic acids such as, for example, hydrochloric orphosphoric acids, or such organic acids as acetic, oxalic, tartaric,mandelic, and the like. Salts formed from free carboxyl groups may alsobe derived from inorganic bases such as, for example, sodium, potassium,ammonium, calcium, or ferric hydroxides, and such organic bases asisopropylamine, trimethylamine, 2-ethylamino ethanol, histidine,procaine, and the like.

These formulations will typically contain a “therapeutically effectiveamount” of the active ingredient, that is, an amount capable ofeliciting an immune response or capable of eliciting a neutralizingresponse, in a subject to which the composition is administered. In thetreatment and prevention of C. parvum infection, for example, a“therapeutically effective amount” would preferably be an amount thatenhances resistance of the mammal in question to new infection and/orreduces the clinical severity of the disease. Such protection will bedemonstrated by either a reduction or lack of symptoms normallydisplayed by an infected host and/or a quicker recovery time.

The exact amount is readily determined by one skilled in the art usingstandard tests and in view of the teachings of the specification. Theantigenic polypeptide, antibody concentration or polynucleotideconcentration will typically range from about 1% to about 95% (w/w) ofthe composition, or even higher or lower if appropriate. Typically,vaccine formulations will contain between about 1 ug to 1 mg pervaccination dose, although more or less may be used if needed. Repeatvaccination (e.g., boosts) can be administered as deemed necessary, forexample by evaluation of reactive T-cells.

To immunize a subject, the vaccine is generally administeredparenterally, usually by intramuscular injection. Intradermal andtransdermal modes of administration may also be employed. Other modes ofadministration, however, such as subcutaneous, intraperitoneal andintravenous injection, are also acceptable. The quantity to beadministered depends on the animal to be treated, the capacity of theanimal's immune system to synthesize antibodies, and the degree ofprotection desired. Effective dosages can be readily established by oneof ordinary skill in the art through routine trials establishing doseresponse curves. The subject is immunized by administration of thevaccine in at least one dose, and preferably two doses. Moreover, theanimal may be administered using as many doses as is required tomaintain a state of immunity to infection. Similarly, for othertherapeutic compositions, the polypeptides and/or antibodies can beadministered by injection (intramuscular, intradermal intraperitoneal,intravenous, etc.)

Additional therapeutic formulations which are suitable for other modesof administration include suppositories and, in some cases, aerosol,transdermal, intranasal, oral formulations, and sustained releaseformulations. For suppositories, the vehicle composition will includetraditional binders and carriers, such as, polyalkaline glycols, ortriglycerides. Such suppositories may be formed from mixtures containingthe active ingredient in the range of about 0.5% to about 10% (w/w),preferably about 1% to about 2%. Oral vehicles include such normallyemployed excipients as, for example, pharmaceutical grades of mannitol,lactose, starch, magnesium, stearate, sodium saccharin cellulose,magnesium carbonate, and the like. These oral vaccine compositions maybe taken in the form of solutions, suspensions, tablets, pills,capsules, sustained release formulations, or powders, and contain fromabout 10% to about 95% of the active ingredient, preferably about 25% toabout 70%.

Intranasal formulations will usually include vehicles that neither causeirritation to the nasal mucosa nor significantly disturb ciliaryfunction. Diluents such as water, aqueous saline or other knownsubstances can be employed with the subject invention. The nasalformulations may also contain preservatives such as, but not limited to,chlorobutanol and benzalkonium chloride. A surfactant may be present toenhance absorption of the subject proteins by the nasal mucosa.

Controlled or sustained release formulations are made by incorporatingthe polynucleotide and/or protein (e.g., antigenic polypeptide orantibody) into carriers or vehicles such as liposomes, nonresorbableimpermeable polymers such as ethylenevinyl acetate copolymers andHytrel® copolymers, swellable polymers such as hydrogels, or resorbablepolymers such as collagen and certain polyacids or polyesters such asthose used to make resorbable sutures. The antigenic polypeptides canalso be delivered using implanted mini-pumps, well known in the art.

The polynucleotides, antigenic polypeptides and/or antibodies of theinstant invention can also be administered via a carrier virus whichexpresses the same. Carrier viruses which will find use with the instantinvention include but are not limited to the vaccinia and other poxviruses, adenovirus, and herpes virus. By way of example, vaccinia virusrecombinants expressing the novel proteins can be constructed asfollows. The DNA encoding the particular protein is first inserted intoan appropriate vector so that it is adjacent to a vaccinia promoter andflanking vaccinia DNA sequences, such as the sequence encoding thymidinekinase (TK). This vector is then used to transfect cells which aresimultaneously infected with vaccinia. Homologous recombination servesto insert the vaccinia promoter plus the gene encoding the instantprotein into the viral genome. The resulting TK-recombinant can beselected by culturing the cells in the presence of 5-bromodeoxyuridineand picking viral plaques resistant thereto.

Thus, one route of administration involves nucleic acid immunization.Thus, nucleotide sequences (and accompanying regulatory elements)encoding the subject antigenic polypeptides and/or antibodies orfragments thereof can be administered directly to a subject for in vivotranslation thereof. Alternatively, gene transfer can be accomplished bytransfecting the subject's cells or tissues ex vivo and reintroducingthe transformed material into the host. Nucleic acids (e.g., DNA andRNA) can be directly introduced into the host organism, i.e., byinjection (see U.S. Pat. Nos. 5,580,859 and 5,589,466; InternationalPublication No. WO/90/11092; and Wolff et al. (1990) Science247:1465-1468). Liposome-mediated gene transfer can also be accomplishedusing known methods. See, e.g., U.S. Pat. No. 5,703,055; Hazinski et al.(1991) Am. J. Respir. Cell Mol. Biol. 4:206-209; Brigham et al. (1989)Am. J. Med. Sci. 298:278-281; Canonico et al. (1991) Clin. Res. 39:219A;and Nabel et al. (1990) Science 249:1285-1288. Targeting agents, such asantibodies directed against surface antigens expressed on specific celltypes, can be covalently conjugated to the liposomal surface so that thenucleic acid can be delivered to specific tissues and cells susceptibleto infection. As noted above, nucleic acid formulations can beadministered by any suitable mode, for example, intramuscularly,intradermally or transdermally.

Diagnostic Assays

As explained above, the polynucleotides and/or antigenic polypeptides ofthe present invention may also be used as diagnostics to detect thepresence of reactive antibodies of C. parvum in a biological sample inorder to determine the presence of C. parvum infection. For example, thepresence of antibodies reactive with antigenic polypeptides can bedetected using standard electrophoretic and immunodiagnostic techniques,including immunoassays such as competition, direct reaction, or sandwichtype assays. Such assays include, but are not limited to, Western blots;agglutination tests; enzyme-labeled and mediated immunoassays, such asELISAs; biotin/avidin type assays; radioimmunoassays;immunoelectrophoresis; immunoprecipitation, etc. The reactions generallyinclude revealing labels such as fluorescent, chemiluminescent,radioactive, enzymatic labels or dye molecules, or other methods fordetecting the formation of a complex between the antigen and theantibody or antibodies reacted therewith.

The aforementioned assays generally involve separation of unboundantibody in a liquid phase from a solid phase support to whichantigen-antibody complexes are bound. Solid supports which can be usedin the practice of the invention include substrates such asnitrocellulose (e.g., in membrane or microtiter well form);polyvinylchloride (e.g., sheets or microtiter wells); polystyrene latex(e.g., beads or microtiter plates); polyvinylidine fluoride; diazotizedpaper; nylon membranes; activated beads, magnetically responsive beads,and the like.

Typically, a solid support is first reacted with a solid phase component(e.g., one or more antigenic polypeptides) under suitable bindingconditions such that the component is sufficiently immobilized to thesupport. Sometimes, immobilization of the antigen to the support can beenhanced by first coupling the antigen to a protein with better bindingproperties. Suitable coupling proteins include, but are not limited to,macromolecules such as serum albumins including bovine serum albumin(BSA), keyhole limpet hemocyanin, immunoglobulin molecules,thyroglobulin, ovalbumin, and other proteins well known to those skilledin the art. Other molecules that can be used to bind the antigens to thesupport include polysaccharides, polylactic acids, polyglycolic acids,polymeric amino acids, amino acid copolymers, and the like. Suchmolecules and methods of coupling these molecules to the antigens, arewell known to those of ordinary skill in the art. See, e.g., Brinkley,M. A. Bioconjugate Chem. (1992) 3:2-13; Hashida et al., J. Appl.Biochem. (1984) 6:56-63; and Anjaneyulu and Staros, International J. ofPeptide and Protein Res. (1987)30:117-124.

After reacting the solid support with the solid phase component, anynon-immobilized solid-phase components are removed from the support bywashing, and the support-bound component is then contacted with abiological sample suspected of containing ligand moieties (e.g.,antibodies toward the immobilized antigens) under suitable bindingconditions. After washing to remove any non-bound ligand, a secondarybinder moiety is added under suitable binding conditions, wherein thesecondary binder is capable of associating selectively with the boundligand. The presence of the secondary binder can then be detected usingtechniques well known in the art.

More particularly, an ELISA method can be used, wherein the wells of amicrotiter plate are coated with a antigenic polypeptide. A biologicalsample containing or suspected of containing anti-antigenic polypeptideimmunoglobulin molecules is then added to the coated wells. After aperiod of incubation sufficient to allow antibody binding to theimmobilized antigen, the plate(s) can be washed to remove unboundmoieties and a detectably labeled secondary binding molecule added. Thesecondary binding molecule is allowed to react with any captured sampleantibodies, the plate washed and the presence of the secondary bindingmolecule detected using methods well known in the art.

Thus, in one particular embodiment, the presence of bound anti-C. parvumantigen ligands from a biological sample can be readily detected using asecondary binder comprising an antibody directed against the antibodyligands. A number of anti-mammalian immunoglobulin (Ig) molecules areknown in the art which can be readily conjugated to a detectable enzymelabel, such as horseradish peroxidase, alkaline phosphatase or urease,using methods known to those of skill in the art. An appropriate enzymesubstrate is then used to generate a detectable signal. In other relatedembodiments, competitive-type ELISA techniques can be practiced usingmethods known to those skilled in the art.

Assays can also be conducted in solution, such that the antigenicpolypeptides and antibodies specific for those proteins form complexesunder precipitating conditions. In one particular embodiment, antigenicpolypeptides can be attached to a solid phase particle (e.g., an agarosebead or the like) using coupling techniques known in the art, such as bydirect chemical or indirect coupling. The antigen-coated particle isthen contacted under suitable binding conditions with a biologicalsample suspected of containing antibodies for the antigenicpolypeptides. Cross-linking between bound antibodies causes theformation of particle-antigen-antibody complex aggregates which can beprecipitated and separated from the sample using washing and/orcentrifugation. The reaction mixture can be analyzed to determine thepresence or absence of antibody-antigen complexes using any of a numberof standard methods, such as those immunodiagnostic methods describedabove.

In yet a further embodiment, an immunoaffinity matrix can be provided,wherein a polyclonal population of antibodies from a biological samplesuspected of containing anti-C. parvum molecules is immobilized to asubstrate. In this regard, an initial affinity purification of thesample can be carried out using immobilized antigens. The resultantsample preparation will thus only contain anti-C. parvum moieties,avoiding potential nonspecific binding properties in the affinitysupport. A number of methods of immobilizing immunoglobulins (eitherintact or in specific fragments) at high yield and good retention ofantigen binding activity are known in the art. Not being limited by anyparticular method, immobilized protein A or protein G can be used toimmobilize immunoglobulins.

Accordingly, once the immunoglobulin molecules have been immobilized toprovide an immunoaffinity matrix, labeled antigenic polypeptides arecontacted with the bound antibodies under suitable binding conditions.After any non-specifically bound antigen has been washed from theimmunoaffinity support, the presence of bound antigen can be determinedby assaying for label using methods known in the art.

Additionally, antibodies raised to the antigenic polypeptides, ratherthan the antigenic polypeptides themselves, can be used in theabove-described assays in order to detect the presence of antibodies tothe proteins in a given sample. These assays are performed essentiallyas described above and are well known to those of skill in the art.

Assays specifically involving the polynucleotides of the presentinvention also include, but are not limited to, assays for alteration ofmRNA levels and/or the presence of polynucleotides which selectivelyhybridize to the sequences described herein. In assay for an alterationin mRNA levels, nucleic acid contained in the samples (e.g., cell ortissue prepared from the subject) is first extracted according tostandard methods, for example using lytic enzymes or chemical solutionsaccording to the procedures set forth in Sambrook et al, supra orextracted by nucleic-acid-binding resins following the manufacturer'sinstructions. The extracted mRNA is then detected by hybridization(e.g., Northern blot analysis) and/or amplification (e.g., PCR). Nucleicacids having at least 10 nucleotides, preferably between about 20 and 25nucleotides, even more preferably between about 50 and 100 nucleotides,and exhibiting sequence complementarity or homology to thepolynucleotides described herein find utility as hybridization probes.It is understood that probes need not be identical, but are typically atleast about 80% identical to the homologous region of comparable size,more preferably 85% identical and even more preferably 90-95% identical.In certain embodiments, it will be advantageous to use nucleic acids incombination with appropriate means, such as a detectable label, fordetecting hybridization. A wide variety of appropriate indicators areknown in the art including, fluorescent, radioactive, enzymatic or otherligands (e.g., avidin/biotin). Further, the nucleic acids can also beattached to a solid support (e.g., glass or chip) for use in highthroughput screening assays using methods described, for example, inU.S. Pat. Nos. 5,405,783, 5,578,832 and 5,445,934. Results of highthroughput assays can be analyzed using computer software programsavailable from the manufacturers.

The above-described assay reagents, including the antigenicpolypeptides, or antibodies thereto, can be provided in kits, withsuitable instructions and other necessary reagents, in order to conductimmunoassays as described above. The kit can also contain, depending onthe particular immunoassay used, suitable labels and other packagedreagents and materials (i.e. wash buffers and the like). Standardimmunoassays, such as those described above, can be conducted usingthese kits.

Below are examples of specific embodiments for carrying out the presentinvention. The examples are offered for illustrative purposes only, andare not intended to limit the scope of the present invention in any way.

C. Experimental Example 1 Isolation and Cloning of C. parvum ag1 and ag2

A. Collection of Oocysts

Neonatal calves were infected with a human isolate of C. parvum obtainedfrom Cadham Provincial Laboratories (Winnipeg, MB, Canada) and the fecescollected and stored in an equal volume of 2.5% potassium dichromate at4° C. Oocysts were isolated from feces by sucrose floatationcentrifugation followed by ultracentrifugation on cesium chloride stepgradients as previously described in Taghi-Kilani et al. (1990) J.Immunol. 145:1571-1576. Purified oocysts were then stored at 4° C. forfuture use.

B. cDNA Expression Library Construction

RNA was extracted from oocysts using a guanidium isothiocyanateisolation procedure as previously described in Rajkovic et al. (1989)PNAS USA 86:8217-8221 and polyadenylylated RNA (poly A+) was isolated byoligo dT selection. Five ml of highly purified oocysts yieldedapproximately 4.8 mg of total RNA and about 20 μg of polyadenylylatedRNA (poly A+ RNA)(mRNA) isolated using oligo dT selection (0.4%).

Five μg of poly A+ RNA was then converted to cDNAs according to themanufacturers instructions (Stratagene, La Jolla, Calif.). To constructthe library, the cloning vector Lambda ZAP IIXROD® (Stratagene), aLambda gill derivative containing the lacz gene (11-galactosidase) andlac promoter, was used. The cDNAs were ligated into the lambda arms,packaged in vitro and plated on E. coli strain SURE® Ligation efficiencywas determined by blue/white color selection of plaques in the presenceof 5-bromo-4-chloro-3-indoyl-11D-galctosidase (X-gal) and2-isopropyl-b-D-thiogalactopyranoside (IPTG). This procedure yielded2×10⁶ primary phage of which 95% were demonstrated to be recombinant byblue-white colour selection in the presence of IPTG/X-gal.

C. Preparation of Human Immune Serum

Human immune serum was obtained from a patient who had aparasitologically documented infection. Antibodies directed against E.coli proteins were removed by preabsortion with a lysate of E. coliX-BLUE®-buffered saline (20 mM TRIS pH 7.5). Serum was diluted 1:200with 0.1% BSA in Tris 500 mM NACl) and incubated overnight at 4° C. withshaking in the presence of 5 mg/ml of the host E. coli strain protein.The debris was pelleted and the supernatant removed. Immunoblots of C.parvum and E. coli were performed to ensure E. coli antibodies had beenremoved and C. parvum antibodies were still present (described below).This prepared immune sera was used in the subsequent screening of thecDNA library.

D. Immunoblotting of Proteins

Following electrophoresis on 10% SDS-PAGE, C. parvum, E. coli orrecombinant cryptosporidial proteins were transferred (Transbiot SDSemi-dry Electrophoretic Transfer Cell/Bio-Rad, Mississauga, Ontario)onto Immobilon-P transfer membranes (Millipore, Bedford, Ma) accordingto the manufacturer' instructions. Five percent (5%) skim milk inTRIS-buffered saline (TBS) was used to block the immunoblots for 2 hoursat 37° C. and then incubated with immune sera diluted 1:200 ormonoclonal antibodies diluted 1:2000 in 0.1% bovine serum albumin(BSA)/TBS for 2 hour's at 37° C. The membranes were washed 3 times for 5minutes each in 0.05% Tween-20 in TBS (TBST). IgG antibodies weredetected using either goat anti-human or anti-mouse IgG conjugated tohorseradish peroxidase (Jackson Immunoresearch Laboratories, West Grove,Pa.) diluted 1:3000 with 0.1% BSA/TBS for 2 hours at 37° C. Followinganother wash, blots were developed in 1.4 mM diaminobenzidine, 8.8 mMcobalt chloride and 0.85 mM hydrogen peroxide.

Immunoblots of C. parvum and E. coli proteins were performed withpreabsorbed immune serum. Predominant bands were located at 23, 33, 45,and >66 kilodaltons, similar to the spectrum of antigens reported byother investigators. Antibodies against E. coli proteins were present inunabsorbed sera but were effectively removed by the absorption procedureleaving cryptosporidial specific antibodies intact.

E. Screening of the Expression Library

A cDNA expression library was screened as follows: approximately 2000primary plaques per plate were incubated for four hours onLuria-Brunelli (LB) agar at 37° C. and the plates were overlaid withnitrocellulose filters (Millipore, Bedford, Mass.) presoaked in 10 mMIPTG and incubated for another four hours at 37° C. Filters were removedand duplicate filters were placed and allowed to incubate for four morehours. The filters were blocked in 5% skim milk in TBST and developed asdescribed above for immunoblotting. Positive clones were plaquepurified.

After library amplification, approximately 650,000 primary plaques werescreened and eight positive clones identified. These were plaquepurified and rescued by in vivo excision into the sequencing phagemidpbluescript SK+.

F. In Vivo Excision and Sequencing of C. Parvum cDNA RecombinantpBluescript SK+ containing the C. parvum cDNA was prepared by an in vivoexcision protocol supplied by the manufacturer (Stratagene, La Jolla,Calif.). Plasmid DNA was prepared by established protocols. Insert cDNAwas sequenced by the dideoxy method (Sequenase™, U.S. Biochemical,Cleveland, Ohio).

The cDNA inserts of the positive clones were completely sequenced. Theeight positive clones encoded two distinct antigens, AG1 and AG2. Thecomposite cDNA sequence of the inserts and the predicted open readingframes of the two antigens are presented in FIG. 1.

The incomplete open reading frame of AG1 deduced from a single cDNA andtwo overlapping cDNA clones extended from nucleotides 8-394. The 3′untranslated region was 945 nucleotides long and extended from positions395-1338. Consensus polyadenylylation signals were located atnucleotides 1233-1238 and 1273-1278. Imperfect polyadenylylation signalswere also identified at nucleotides 1241-1245 and 1307-1311. Thepredicted open reading frame encoded a peptide of 129 amino acids with apredicted molecular weight of 15 Kd. The predicted isoelectric point wasPh 9.6 with 44% of the amino acids being hydrophobic. Two N-linkedglycosylation sites were identified at residues 36-38 and 71-73.

The incomplete composite open reading frame of AG2 deduced from fiveoverlapping cDNA clones extended from nucleotides 9-587. The 3′untranslated region was 712 nucleotides in length and extended fromnucleotides 588-1298. A number of imperfect consensus polyadenylylationsignals were identified, for instance at nucleotides 945-949 and1141-1145. The predicted open reading frame encoded a peptide of 193amino acids in length with a predicted molecular weight of 21.8 Kd. Thepredicted isoelectric point is pH 6.23 and 36% of the amino acids werehydrophobic. Two N-linked glycosylation sites were identified atresidues 36-38 and 51-53.

The GenBank database was searched using the BLAST program (see, e.g.,Altschul et al. (1997) 25:3389-3402), using for example, the followinggap penalties: existence: 11 or 5, extension: 1 or 2. Default parameterscould also be used. The searches did not identify proteins that exhibitsequence identity with AG1 or AG2.

Example 2 Expression of the C. parvum cDNAs in E. coli and Analysis byImmunoblotting

Two different prokaryotic expression vector systems were used togenerate recombinant protein, pGEX-2T™ (Pharmacia Biotech, Montreal,Canada) and pET-11A™ (Novagen, Madison, Wis.). The cDNA inserts of thetwo antigens (AG1 and AG2) were subcloned as a SmaI/XhoI end-filledfragment into the SmaI site of the pGEX-2T vector, and transformed intoE coli strain DH5-α. Fusion proteins were induced in the presence of 0.5mM IPTG and the bacterial cells harvested for further analysis accordingto standard protocols, for example as described in Smith et al. (1988)Gene 67:31-40.

In order to subclone the AG1 cDNA insert into pET-11A, oligonucleotideprimers corresponding to the 5′ (AG1 5′-PCR,5′-GTCATATGGCACGAGAATTACCATCTGAT-3′) (SEQ ID NO:5) and complementary tothe 3′(AG1 3′-PCR, 5′-GACATATGTTAATTTCTCATTTGTACTTG-3′) (SEQ ID NO:6)ends of the cDNA, containing engineered NdeI sites, were synthesized fordirect DNA amplification. The amplification was carried out in thepresence of Taq polymerase (Perkin Elmer Cetus, Rexdale, Ontario) in astandard 100 ml PCR reaction mixture containing 1.0 μg template, 100 mMof each primer and 0.2 mM dNTPs for 30 cycles at 94° C. (1 min), 50° C.(1 min), and 72° C. (1 min) according to the manufacturer's instructions(Perkin Elmer Cetus, Rexdale, Ontario). The amplified cDNA was digestedwith Nde1. The isolated insert was subcloned into the NdeI site ofpET-11A and transformed in E. coli DH5-α. Plasmids containing insertswere electroporated into E. coli expression strain BL21/IDE3/plyS(Novagen, Madison, Wis.) and fusion proteins were induced in thepresence of 0.5 mM IPTG and the bacterial cells harvested for proteinanalyses using routine protocols, for example as described in Studier etal. (1990) Methods Enzymol. 185:60-89.

Expression of C. parvum recombinant protein by the PGEX and pET vectorswas evaluated by polyacrylamide gel electrophoresis and coomaissiestaining followed by immunoblotting onto Immobilon-P transfer membranesusing standard techniques, for example as described in Sambrook et al,supra. Immunoblots containing induced and uninduced proteins wereblocked with 5% skim milk in TBST overnight at 4° C. Recombinant proteinwas detected using preabsorbed human immune sera prepared as describedabove.

The predicted size of the AG1 fusion protein withglutathione-s-transferase using the pGEX-2T vector was 43 Kd. AnSDS-PAGE analysis of induced versus induced proteins produced aninsoluble band as predicted at approximately 43 Kd and an additionalinsoluble band of lesser intensity at approximately 66 Kd. Both bandswere recognized on immunoblot by human immune sera and monoclonalantibodies generated against the 43 Kd band purified by gelelectrophoresis and electroelution. When AG1 was expressed in the pET11A vector, an insoluble band of the predicted size of about 20 Kd wasproduced and was recognized by human immune sera and monoclonalantibody.

The predicted size of the AG2 fusion protein withglutathione-S-transferase using pGEX-2T vector was approximately 46 Kd.An SDS-PAGE analysis of induced versus uninduced protein failed toproduce a recombinant fusion protein band at the expected molecularweight but produced an easily visualized insoluble band at 98 Kd.Immunoblot analysis with human immune serum and with monoclonal antibodygenerated against the purified 98 Kd band revealed the presence of aweak band at approximately 44 Kd and an intense band at 98 Kd. Thesebands did not appear in the uninduced control lanes. Sequencing of theexpression vector confirmed the size of the predicted open readingframe.

Example 3 Production and Purification of Antibodies from Human Serum

Recombinant cryptosporidial proteins expressed as GST fusion proteinswere purified by preparative gel electrophoresis and electroelution andused to immunize BalbC mice. Mice were immunized intraperitoneally threetimes at four week intervals with 50 mg of purified recombinant antigenin RIBI™ adjuvant (RIBI ImmunoChem Research Inc., Hamilton, Mont.). Afinal boost of 50 mg of purified recombinant antigen in phosphatebuffered saline was given by intravenous injection. Three days later theanimals were sacrificed and the spleens harvested. Splenocytes werefused with NS-1 using PEG (Gibco) and cultured in 96 well plates asdescribed in Studier et al, supra. Positive hybridomas were selected byenzyme immunoassay (EIA) in which wells were coated with purifiedrecombinant antigen expressed in the pET 11A vector (AG1), or doublyscreened with purified recombinant GST fusion protein and GST (AG2) toidentify cryptosporidial specific hybridomas according to standardprotocols, e.g., Wilkins et al. (1996) J. Biol. Chem. 271:3046-3051.

Purified recombinant cryptosporidial antigens were resolved byelectrophoresis, transferred to Immobilon-P membranes, and immunobloftedwith human immune sera diluted 1:200 in PBS. Antibodies were acid elutedas previously described (see, e.g., Peterson et al., (1990) Infect.Immun. 60:2343-2348), concentrated by centrifugation in a Centricon-10apparatus (Amicon Inc., Beverly, Mass.) to a final volume of 0.5 ml inPBS according to the manufacturer's instructions, and used to immunoblotcryptosporidial proteins as described above.

A total of 12 individual monoclonal antibodies were isolated whichreacted with the AG1 PETII purified recombinant fusion proteinspecifically in an EIA. Four monoclonal antibodies were identified whichreacted specifically with the cryptosporidial fusion portion of the AG2GST fusion protein. Two monoclonal antibodies, 1101 directed against Ag1and 222 directed against AG2, were selected for further study based ontheir reactivity by Immonoblot with native proteins and EIA againstrecombinant protein.

The immunoblots of affinity purified human antibodies and monoclonalantibody 1101 (AG1) directed against soluble and insolublecryptosporidial proteins are presented in FIGS. 3A and 3B, respectively.Human antibodies eluted from the AG1 GST fusion protein recognized afaint band in total cryptosporidial protein at approximately 22 Kd (FIG.3A), while monoclonal antibody 1101 generated against the AG1 GST fusionprotein recognized a faint 22 Kd band in insoluble cryptosporidialprotein (FIG. 3B lane 1) and three bands at approximately 22, 32, and 96Kd in soluble cryptosporidial protein (FIG. 3B lane 2).

The immunoblots of affinity purified human antibodies and monoclonalantibody 222 (AG2) directed against soluble and insolublecryptosporidial proteins are presented in FIGS. 4A and 4B, respectively.Human antibodies eluted from the AG2 GST fusion protein recognized threebands in total cryptosporidial protein at approximately 17, 34, and 84Kd (FIG. 4A) while monoclonal antibody 222 generated against the AG2 GSTfusion protein recognized no bands in insoluble cryptosporidial protein(FIG. 4B lane 1) and five bands at approximately 6, 10, 22, 34 and 84 Kdin soluble cryptosporidial protein (FIG. 4B lane 2). The intense band at55 Kd in FIG. 4B lanes 1 and 2 was artifactual.

Example 4 In Situ Localization

Previously purified oocysts were washed three times in PBS andresuspended at a density of 5×10⁷ oocysts/ml and either used directly orexcysted to generate sporozoites as previously described in Example 5A.Sporozoites were quantitated by hemocytometry prior to use.Approximately 0.5×10⁶ oocysts or sporozoites were aliquoted onto slidesand allowed to air dry at 37° C. Slides were fixed for 10 min in 100%methanol, dried, and washed three times in PBS. Slides were blocked in1% BSA/0.1% sodium azide in PBS for 1 hr. at 40° C., washed 3× in PBSand incubated with primary monoclonal antibody at 5 mg/ml in PBS/1%BSA/0.1% sodium azide for 1 hr at 40° C. After washing 3× in PBS, 1:100dilution of secondary antibody (1.4 mg/ml-Rhodamine goat anti-mouseantisera (Jackson Immunoresearch Laboratories, West Grove, Pa.) in thesame buffer was added and incubated for 1 hr in the dark at 40° C. Theslides were washed 3× in PBS and fluorescence was detectedmicroscopically (Olympus BH5 Model BH2 PM-10ADS) and documentedphotographically (Kodak Provia 1600).

The results of immunolocalization of monoclonal antibodies 1101 (AG1)and 222 (AG2) against oocysts and sporozoites are presented in FIGS. 5A,B, C and 5D, E and F, respectively. Monoclonal antibody JB1 directedagainst human integrin non specifically labelled debris in the slide(FIG. 5A). Monoclonal antibody 1101 directed against AG1 intenselystained in a diffuse pattern single and pairs of oocysts (FIG. 5B).Monoclonal antibody 222 directed against AG2 stained single oocysts andclumps with a ring-like pattern (FIG. 5C). Sporozoites were notvisualizable with monoclonal antibody JB1 (FIG. 5D). Monoclonal antibody1101 detected sporozoites with an even staining pattern (FIG. 5E), whilemonoclonal antibody 222 detected sporozoites with an intense pattern(FIG. 5F).

Example 5 Neutralizing Effect of Monoclonal Antibodies

A. Purification of C. parvum Sporozoites

Oocysts were suspended at 5.0×10⁷/ml in Hank's balanced salt solutionand incubated at 37° C. for 1.5 hours to release sporozoites.Sporozoites were purified on a DEAE-cellulose column equilibrated at 4°C. overnight in column buffer (80 mM Na₂HPO₄, 58 mM NaCl, 55 mMglucose). Excysted sporozoites were washed twice in column buffer,pelleted at 3500×G, and resuspended in 20 ml of column buffer. Thepelleted sporozoites were applied to one cm of matrix suspended in aEcono-column (BioRad). 50 ml of column buffer were used to elute thesporozoites which were pelleted and washed twice with Hank's Balancedsalt solution. Sporozoites were quantitated by hemocytometry and theconcentration adjusted to yield a final concentration of 0.5×10⁶/ml.

B. In Vitro Invasion assay

HT-29 cells were obtained from the American Tissue Culture Collection.Cells were originally cultured in Dulbecco's Modified Eagle Medium(DMEM) plus glutamine (Gibco-BRL) supplemented with 10% fetal calf serum(Intergen) in a 5% CO₂ atmosphere. Prior to use in the in vitro invasionassay, cells were transitioned from DMEM to Leibovitz's L-15 medium(Gibco-BRL), 10% fetal calf serum and 5 μg/mlpenicillin/streptomycin(Gibco-BRL)) in a 5% CO₂ atmosphere and passaged30 times to permit differentiation in the glucose free medium aspreviously described, for example in Flanigan et al. (1991) Infect.Immun. 59:234-239.

Three monoclonal antibodies were used in these experiments. Monoclonalantibody 1101 is an IgG directed against cryptosporidial antigen 1 (AG1)and monoclonal antibody 222 is an IgG directed against cryptosporidialantigen 2 (AG2). As described above, both monoclonal antibodies detectnative protein on immunoblot, react with recombinant protein in EIA, andlocalize to oocysts and sporozoites in immunofluorescence studies.Monoclonal antibody 2FI2 is a negative control IgG antibody directedagainst the lipooligosaccharide surface of the bacterium Hemophilusducreyi (provided by Dr. Ian McClean). For the assay, cells were grownon cover slips to approximately 80% confluency and exposed to 5×10⁵sporozoites in addition to titrating doses of monoclonal antibodies asfollows: monoclonal antibodies 1101, 222 and 2F12 at concentrations of0, 1, 2, 4, 8, 10, 20, 40, 80 μg/ml of culture medium. To determine ifneutralization effects were additive or synergistic antibodies wereadded in combination at a final concentration of 4 μg/ml of eachmonoclonal antibody as follows: 1101, 222, 2F12; 1101+222; 2F12+222;2F12+1101.

Exposed cells were cultured for 48-72 hours, fixed in 100% methanol, andstained for evaluation by Hematoxylin and Eosin as previously described,for example in Cotran et al. “Pathological Basis of Disease” (1998),W.B. Saunders Co. Each experiment was performed in triplicate and thenumber of infected cells per 25 fields on each slide determined by lightmicroscopy. Differences were determined to be significant usingT-testing in the Statistical Package for Social Sciences (SPSS)statistical program, available, for example, on the World Wide Web.

The effect of increasing concentrations of monoclonal antibodies 1101and 222 compared to control monoclonal antibody 2F12 on sporozoiteinvasion of HT-29 cells is presented in Table 1 and graphically in FIG.6.

TABLE 1 Comparison of neutralization activity of monoclonals 1101 and222 versus 2F12 in a HT-29 invasion assay. Mean ± SD Infected cells Mab25 Fields P value 0 ug/ml 2F12 29.3 ± 2.5 1101 29.3 ± 2.5 ns  222 23.0 ±3.6 ns 1 ug/ml 2F12 30.0 ± 4.6 1101 24.7 ± 3.5 ns  222  4.3 ± 0.6 0.0012 ug/ml 2F12 30.0 ± 6.0 1101 13.3 ± 2.9 0.012  222  5.7 ± 3.1 0.003 4ug/ml 2F12 29.7 ± 2.9 1101  8.0 ± 1.0 0.003  222  4.7 ± 1.5 0.000 8ug/ml 2F12 28.7 ± 3.5 1101 11.0 ± 3.0 0.003  222  5.0 ± 3.0 0.001 10ug/ml 2F12 26.7 ± 7.5 1101 13.0 ± 6.1 0.070  222  8.0 ± 2.0 0.014 20ug/ml 2F12 25.3 ± 2.5 1101  8.7 ± 2.5 0.001  222  7.3 ± 1.5 0.000 40ug/ml 2F12 27.3 ± 4.5 1101 11.3 ± 4.1 0.011  222  4.7 ± 1.5 0.001 80ug/ml 2F12 26.3 ± 6.8 1101 15.3 ± 4.5 0.080  222  5.3 ± 0.6 0.006

The reduction in infectivity for AG 1 monoclonal antibody 1101 becamesignificant at 2 ug/ml although at 10 and 80 μg/ml statisticalsignificance was not achieved. Over all the range of concentrationstested, monoclonal antibody 1101 resulted in a 53% reduction ofinfectivity which was highly significant (p<0.001). Monoclonal antibody222 directed against AG2 had a more dramatic and sustained neutralizingactivity when compared to monoclonal 1101. Over the range 1-80 μg/mlneutralization was observed. The mean reduction in infectivity resultingfrom the presence of monoclonal 222 was 80% which was highly significant(p<0.0001).

To determine if the neutralizing effects of the monoclonal antibodieswere additive, synergistic, or competitive, combinations were assayedmaintaining the concentration of each added monoclonal antibody at 4μg/ml, a level at which differences were consistently significant. Theresults of these studies are presented graphically in FIG. 7.

The addition of monoclonal antibodies 1101 and 222 to the cultures hadno additive or synergistic effect on reduction in infectivity whencompared to either alone or in combination with the non specificantibody 2FI2. Although the reductions in infectivity were significantwhen compared to the negative control (p<0.001) and the non specificantibody 2F12 (p<0.002), there was no discernable interaction betweenany of the antibody combinations on infectivity. In no instance didneutralization reach 100%. This suggests that the mechanism ofinfectivity is saturable for this pathway and perhaps ancillary pathwaysmay be used to achieve invasion. It is also possible that the antibodiesdid not completely block invasion although blocking two differentantigens might be predicted to have an additive effect unless the twoantibodies competed for a similar site in the invasion process.

Thus, the cloning, expression and characterization of C. parvumantigenic polypeptides and antibodies which recognize epitopes on thesepolypeptides are disclosed, as are methods of using the same. Althoughpreferred embodiments of the subject invention have been described insome detail, it is understood that obvious variations can be madewithout departing from the spirit and the scope of the invention asdefined by the appended claims.

A deposit of hybridomas useful in practicing the invention was made withthe American Type Culture Collection, 10801 University Boulevard,Manassas, Va. (deposits received by ATCC May 16, 2000, ATCC PatentDeposit Designations PTA-1879 and PTA-1880).

1. An isolated nucleic acid molecule encoding an immunogenic C. parvumantigenic polypeptide 1 (AG1) comprising the amino acid sequence of SEQID NO:2, or encoding an immunogenic fragment thereof comprising at least15 amino acids and that elicits an equivalent or enhanced immunologicalresponse as compared to the polypeptide comprising the sequence of SEQID NO:2, or encoding a polypeptide with at least 90% sequence identityto a polypeptide comprising the amino acid sequence of SEQ ID NO:2 andthat elicits an equivalent or enhanced immunological response ascompared thereto.
 2. The nucleic acid molecule of claim 1, wherein saidmolecule encodes the amino acid sequence of SEQ ID NO:2.
 3. The nucleicacid molecule of claim 1, comprising the nucleotide sequence of SEQ IDNO:1.
 4. A recombinant vector comprising: (a) a nucleic acid moleculeaccording to claim 1; and (b) control elements that are operably linkedto said nucleic acid molecule whereby said coding sequence can betranscribed and translated in a host cell, and at least one of saidcontrol elements is heterologous to said coding sequence.
 5. Arecombinant vector comprising: (a) a nucleic acid molecule according toclaim 2; and (b) control elements that are operably linked to saidnucleic acid molecule whereby said coding sequence can be transcribedand translated in a host cell, and at least one of said control elementsis heterologous to said coding sequence.
 6. A recombinant vectorcomprising: (a) a nucleic acid molecule according to claim 3; and (b)control elements that are operably linked to said nucleic acid moleculewhereby said coding sequence can be transcribed and translated in a hostcell, and at least one of said control elements is heterologous to saidcoding sequence.
 7. A host cell transformed with the recombinant vectorof claim
 4. 8. A host cell transformed with the recombinant vector ofclaim
 5. 9. A host cell transformed with the recombinant vector of claim6.
 10. A method of producing a recombinant C. parvum antigenicpolypeptide comprising: (a) providing a population of host cellsaccording to claim 7; and (b) culturing said population of cells underconditions whereby the antigenic polypeptide encoded by the codingsequence present in said recombinant vector is expressed.
 11. A methodof producing a recombinant C. parvum antigenic polypeptide comprising:(a) providing a population of host cells according to claim 8; and (b)culturing said population of cells under conditions whereby theantigenic polypeptide encoded by the coding sequence present in saidrecombinant vector is expressed.
 12. A method of producing a recombinantC. parvum antigenic polypeptide comprising: (a) providing a populationof host cells according to claim 9; and (b) culturing said population ofcells under conditions whereby the antigenic polypeptide encoded by thecoding sequence present in said recombinant vector is expressed.
 13. Acomposition comprising a pharmaceutically acceptable vehicle and anucleic acid molecule according to claim
 1. 14. A composition comprisinga pharmaceutically acceptable vehicle and a nucleic acid moleculeaccording to claim
 2. 15. A composition comprising a pharmaceuticallyacceptable vehicle and a nucleic acid molecule according to claim 3.